It is well known that various aqueous systems containing metabolizable components, either in trace or major quantities, are normally susceptible to attack and degradation by microorganisms. Examples of such compositions are cutting oils; cosmetics, such as lotions and creams; fuel oil; textile emulsions; latex emulsions and paints; starch-based adhesives; industrial cooling water; emulsion waxes; water used in pulp and paper manufacturing (so-called "process" water, e.g., "white water"); and flood water used in secondary oil recovery methods.
A number of problems and limitations have recently faced those in the art seeking to provide effective antimicrobial preservatives for such aqueous systems. These problems involve concerns about worker exposure and environmental impact. Many current preservatives are effective because they are toxic to microorganisms at low concentrations, e.g., about 100 parts per million (ppm). Human exposure to such preservatives in the parts per million range does not normally pose a health risk. The pure product, however, may pose an unacceptable risk to workers who may be exposed to the pure concentrated material on a daily basis, thereby requiring them to protect themselves from accidental inhalation or accidental skin exposure. A stable, non-hazardous formulation is therefore essential.
One method of keeping the concentration of such antimicrobial agents to an acceptable handling level involves using diluents. Diluents are also desirable to assist in delivering the antimicrobial agents to the medium being preserved. The diluents must, of course, meet certain criteria. For example, they must be compatible with a particular antimicrobial agent and with the medium in which the antimicrobial agent is to be used. They should not be highly flammable nor be toxic, thereby resulting in very few diluents satisfying these criteria at an acceptable price.
More recently, pressures concerning the toxicity of the diluent and its compatibility with the environment have resulted in restricting the number of acceptable diluents available for selection. It is expected that even fewer diluents or carriers will be acceptable in the future. There is a need in the industry to find a diluent or a carrier that meets the following criteria:
The diluent must be compatible with the antimicrobial agent and should not diminish or destroy its antimicrobial activity. PA1 The final product must have a flash point greater than 150.degree. F. in order to avoid dangers due to flammability. PA1 The system must work in the intended medium. PA1 It should not be on List 1 or List 2 of the United States Environmental Protection Agency's (EPA) "Inert Ingredients in Pesticide Products; Policy Statement." Lists 1 and 2 cover inert ingredients of extreme toxicological concern and potential toxicological concern, respectively. PA1 The system must be economically competitive, i.e., it must not be so expensive that the system cannot compete in the market. PA1 The diluent or carrier system should be either odorless or have a pleasant odor. PA1 The antimicrobial agent should be quite soluble in the diluent.
Currently, the BNS product is a blend of Amsco Solv.RTM. F (Stoddard solvent) with and without N,N-dimethyl-formamide (DMF) and is believed to be the only non-oxidizing biocide on the market with a flammable warning label. Amsco Solv.RTM. F is 70% heavy aromatic hydrocarbons and 30% aliphatic hydrocarbons. The mixture of Amsco Solv.RTM. F and DMF has several undesirable characteristics. Both solvents have low boiling points and flash points: Amsco Solv.RTM. F (bp 178.degree.-214.degree. C.; FP 61.degree. C.) and DMF (bp 153.degree. C.; FP 58.degree. C.). The Amsco Solv.RTM. F. and DMF blend also has an very undesirable odor, which has caused customers to discontinue the product.
Additionally, DMF has many undesirable properties, including causing skin irritation, stomach pains, vomiting, diarrhea, nausea, dizziness and headaches in humans. Acute effects of exposure to DMF may be caused by inhalation, ingestion, or skin absorption. Vapor or mist from DMF is irritating to the mucous membranes and upper respiratory tract. Dimethylformamide may also cause testicular cancer. Its use in pulp and paper manufacturing has all but ceased in the United States because it is on EPA's List 1, i.e., inert ingredients of extreme toxicological concern. Further, the oral LD.sub.50 (rats) is 2.8 g/kg and the dermal LD.sub.50 (rabbits) is 4720 mg/kg. The 6-hour inhalation ALC (rats) is 5000 ppm.
Although, for certain applications, a solid carrier system for BNS has been acceptable, in most instances a solvent system with desirable physical, chemical, environmental, and toxicological properties is needed. The present invention overcomes the disadvantages of prior compositions by providing compositions displaying the desirable characteristics outlined above.